CHEMISTRY PAPER 233/1 K.C.S.E 2002

QUESTIONS

1) Name One property of neon that makes it possible to be used in electric lamps

2) Oxygen and sulphur belong to group (VI) of the periodic table. Explain why there is a big

difference their (melting points of oxygen is – 2160C while that of sulphur is 440C.

3) The oxides of elements A and B have the properties shown in the table below. (the letter

do not represent the actual symbols of elements)

A B

Gaseous at room temperature Solid at room temperature

Dissolves in water to form an acidic solution Dissolves in water to form an alkaline solution

Give one example of elements A and B

A

B

4) The following two tests were carried out on chlorine water contained in two test tubes

(a) A piece of blue flower was dropped into the first – tube. Explain why the flower

was bleached

(b) The second test- tube was corked and exposed to sunlight after a few days, it was

found to contain a gas that rekindled a glowing splint. Write an equation for the

reaction which produced the gas

5) (a) Write the electronic configuration of calcium ( atomic number 20 ) and beryllium

(atomic number 4)

(b) Why is calcium more reactive than beryllium

6) When potassium nitrate is heated, it produces potassium nitrate and gas C1

(a) Identify gas C

(b) Name the type of reaction undergone by the potassium nitrate

7) State and explain how the rate of reaction between zinc granules and steam can be

increased

8) The apparatus shown below was set to prepare and collect hydrogen sulphide

(a) Name solid C2

(b) Give a reason why warm water is used

(c) What observation would be made if hydrogen sulphide gas was bubbled into a

solution of lead II nitrate?

9) Use the reactions given below to answer the questions that follow. The letters do not

represent the actual symbols of the elements

D(s) + E2+ (aq) →D2+(aq) + E(s)

D (s) + 2F+(aq) → D2+(aq) + 2F(s)

E (s) + 2 F+ (aq) →E2+ (aq) + 2F(s)

G (s) + →E2+(aq) →G2+(aq) + E(s)

G (s) + D2+ (aq) →no reaction

(a) What name is given to the type of reaction given above?

(b) Arrange the elements D, E, F and G in the order of their reactivity starting with

the most reactive

(c) Complete the equation below

G(s) + 2F+ (aq) →

10) The graph below represents a radioactive decay series for isotope H.

Study it and answer the questions that follow

(a) Name the type of radiation emitted when isotope H changes to isotope J.

(b) Write an equation for the nuclear reaction that occur when isotope J changes to

isotope K

210 210

J k e

81 → 82 + -1

(c) Identify a pair of isotope of an element in the decay series

11) In an experiment, sulphur dioxide gas was bubbled into water followed by chlorine gas.

The resulting clear solution gave a white precipitate when mixed with a acidified barium

chloride solution. Explain these observations

12) Concentrated sulphuric acid was added to iron II sulphate acidified with sulphuric acid

and the mixture heated. The solution turned from pale green to yellow with evolution of

brown gas. Explain these observations.

13) Use the equations below to answer the questions that follow

K(g) + Cl – (g) → KCl (s); ∆ H1 = - 701kJmol-1

KCl (s) →K+(aq) Cl ; ∆H2 = + 15kJmol-1

(a) What is the name of ∆H1?

(b) Calculate the heat change for the process

K(g)+ + Cl- (g) → K+ (aq) + Cl-(aq)

14) Iron is extracted from its ore by the blast furnace process

(a) Name one ore from which iron is extracted

(b) One of the impurities in iron is removed in the form of calcium silicate. Write an

equation for the reaction in which calcium silicate is produced

15) When carbon dioxide gas was passed through aqueous calcium hydroxide a white

suspension was formed

(a) Write an equation for the reaction that took place

(b) State and explain the changes that would occur when carbon dioxide gas is bubbled

through the white suspension

16) With reference to iodine, distinguish between covalent bonds and Van Der Waals forces

17) The structures below represents a portion of a polymer

(a) Give the name of the polymer

(b) Give one industrial use of the polymer

18) Describe how a solid sample of Zin (II) carbonate can be prepared starting with zinc

oxide

19) Bismuth chloride (BiCl3) reacts with water according to the equation given below

BiCl3 (aq) + H2O (l) BiOCl (s) + 2 HCl (aq)

(a) State what would happen when a few drops of dilute hydrochloric acid are added to

the mixture at equilibrium

(b) Give a reason for your answer in (a) above

20) The table below gives some information about the electrical conductivity and the likely

bonding in substances N,P and Q. Complete the table by inserting the missing

information the spaces numbered I, II and III

Substance Likely type of bonding

present

Electrical solid Conductivity

N Metallic I………………… Conducts

P II……………………. Does not conduct Conducts

Q III …………………… Does not conduct Does not conduct

21) In an experiment 30cm3 of 0.1 M sulphuric acid were reacted with 30cm3 of 0.1 M

sodium hydroxide

(a) Write in equation of the reaction that took place

(b) State the observations that were made when both and red litmus

papers were dropped into the mixture

(c) Give a reason for your answer in (a) above

22) The diagram below is set – up for the laboratory preparation of oxygen gas

(a) Name solid R

(b) Write an equation for the reaction that takes place in the flask

(c) Give one commercial use of oxygen

23) When excess lead nitrate solution was added to a solution containing sodium chloride,

the precipitate formed was found to weigh 5.56 g. Determine the amount of sodium

chloride in the solution ( Pb = 207, Cl = 35.5 Na = 23)

Pb (XO3(aq) + 2NaCl (aq) PbCI2 + NaNO3 (aq) (l)

24) (a) Give a reason why concentrated sulphuric acid is not used to dry ammonia gas

(b) Name one suitable drying agent for ammonia gas

25) But -2- ene undergoes hydrogenation according to the equation given below

CH3CH = CHCH3 (g) + H2 (g) →CH3CH2CH2CH3 (g)

(a) Name the product formed when but -2 – ene reacts with hydrogen gas

(b) State one industrial use of hydrogenation

26) The set – up below was used to electroplate a metallic spoon. Study it and answer the

questions that follow

(a) Write an ionic equation for the reaction that occurred at the cathode

(b) State and explain what happened to the anode

27) The following tests were carried out on three separate portions of a colourless solution S

Tests Observations

(i) Addition of dilute hydrochloric acid to the

first portion of solution

No observable change

(ii) addition of aqueous sodium carbonate to the

second portion of solution S

A white precipitate was formed

(iii) Addition of aqueous ammonia to the third portion

of a solution

A white precipitate was formed which dissolved on

addition of excess aqueous ammonia

(a) From the information in test (i), name a cation, which is not present in solution S.

(b) Identify a cation, which is likely to be present in solution S

(c) Write an ionic equation for the reaction, which takes place in test (ii)

CHEMISTRY PAPER 233/2 K.C.S.E 2002

QUESTIONS

1. (a) what method can be used to separate a mixture of ethanol and propanol?

(b) (i) Explain how a solid mixture of sulphur and sodium chloride can be separated

Into solid sulphur and solid chloride

(c) The table below gives the solubilities of potassium bromide and potassium

sulphate at O0C and 400C

Substance Solubility g/100g water at

00C 400C

Potassium bromide 55 75

Potassium sulphate 10 12

When an aqueous mixture containing 60g of potassium and 7 g of potassium sulphate in 10g of

water at 800C was cooled to 00C some crystals were formed

(i) Identify the crystals

(ii) Determine the mass of the crystals formed

(iii) Name the method used to obtain the crystals

(iv) Suggest one industrial application of the method named in (iii) above

2. Study the flow chart below and answer the questions follow

(a) Identify substance

Concentrated

sodium chloride

Chlorine gas Hydrogen gas Substance A

Hydrogen Chloride gas

Chloroethane

PVC

Electrolysis

Substance B

Process C

(i) A

(ii) B

(b) Name process C

(c) Give one use of PVC

(d) Write an equation for the reaction in which chlorine gas is produced

(e) State and explain the observation that would be made if chlorine gas was bubbled into an

aqueous solution of sodium iodide

(f) In the preparation of a bleaching agent (Sodium hypochlorite), Excess chlorine gas was

bubbled into 15 litres of cold 2 m sodium hydroxide

(i) Write an equation for the reaction between chlorine gas and cold dilute sodium

Hydroxide

(ii) Calculate the:

Number of moles of sodium hydroxide used

Mass in kilograms of the sodium hypochlorite produced = 1. 1175

3. (a) Distinguish between exothermic and endothermic reaction ( 2mks)

(b) Changes of state are either exothermic or endothermic

Name a change of state that is:

(i) Endothermic ( 1 mk)

(ii) Exothermic ( 1 mk)

(c) When pure water is heated at 1 atmospheric pressure at sea level, the temperature of the

water does not rise beyond 1000C. Even with continued heated. Explain this observation.

(d) Study the energy cycle diagram below and answer the questions that follow

(i) What does ∆H1 represent?

(ii) Show the relationship between ∆ H1, ∆H2 and ∆H3

(e) Butane and propane are constituents of a cooking gas. Which produces more energy per

mole on combustion? Explain

4. The table below gives standard electrode potentials for the metals represented by the Letters

D, E, F and G. study it and answer the questions that follow.

Metals Standard electrode potential (volts)

D -0.13

E -0.85

F +0.34

G - 0.76

(a) Which metal can be displaced from a solution of its salts by all the other metals in the

table? Give a reason ( 2 mks)

(b) Metals F and G were connected to form a cell as shown in the diagram below

(i) Write the equation for the reactions that occur at electrodes

F

G

(ii) On the diagram, indicate with an arrow the direction in which electrons would flow on

the diagram above

(ii) What is the function of the salt bridge? ( 1 mk)

(c) An electric current was passed through a concentrated solution of copper (II) chloride as

shown in the diagram below

(i) Explain the observation that would be made on the electrolyte as the experiment

progresses ( 2 mks)

(ii) After sometime, test- tube H was found to contain a mixture of two gases. Explain this

observation ( 3 mks)

(iii) Which of the electrodes is the anode? Explain ( 2 mks)

5. (a) Candle wax is mainly a compound consisting of two elements.

Name the two elements ( 2 mks)

(b) The set- up below was used to investigate the burning of a candle study it and answers

the questions that follow

(i) What would happen to the burning candle if the pump was turned off? Give reasons

(ii) State and explain the changes in mass that are likely to occur in tube N by the end of the

experiment ( 3 mks)

(iii) Name two gases that come out through tube M ( 2 mks)

(iv) Name another substance that could be used in the place of calcium oxide in tube N

6. (a) Name one ore from which copper metal is extracted ( 1 mk)

(b) The chart below shows a sequence of reactions starting with copper.

Study it and answer the questions that follow

(i) Identify

Gas P ( 1mk)

Reagent Q ( 1 mk)

Solid R ( 1 mk)

(ii) Write an equation for the reaction that takes place in step 5

(iii) State the observations made in steps 4 and 7 ( 2 mk)

Step 4

Step 7 ( 1mk)

(c) Bronze is an alloy of copper and another metal

(i) Name the other metal ( 1mk)

(ii) Give one use of Bronze ( 1mk)

6. (a) Write the structural formula of:

(i) Methanol

(ii)Methanoic acid ( 1mk)

(b) Write the equation for the reaction between methanoic acid and aqueous

sodium hydroxide ( 1mk)

(c) (i) Name the product formed when methanol reacts with methanoic acid

(ii) State one condition necessary for the reaction in (c) (i) above to take place

(d) (i) Describe one chemical test that can be used to distinguish between hexane and

hexane ( 2 mks)

(ii) State one use of hexane (1mk)

(iii) Hydrogen reacts with hexane to form hexane. Calculate the volume or hydrogen

gas required to convert 42g of hexane to hexane at S.T.P ( C=12.0, H=1.0, molar

gas volume at S.T.P is = 22.4 litres) ( 4 mks)